Problem: $ B = \left[\begin{array}{rrr}1 & 2 & 0 \\ 1 & 2 & 1 \\ 1 & 0 & 2\end{array}\right]$ What is $ B^{-1}$ ?
$ = \left[\begin{array}{rrr}2 & -2 & 1 \\ -\frac{1}{2} & 1 & -\frac{1}{2} \\ -1 & 1 & 0\end{array}\right]$